fix(copilot): keep notifications visible and detect marker via message lookup

src/shared/internal-initiator-marker.ts

@@ -3,11 +3,9 @@ export const OMO_INTERNAL_INITIATOR_MARKER = "<!-- OMO_INTERNAL_INITIATOR -->"
 export function createInternalAgentTextPart(text: string): {
   type: "text"
   text: string
-  synthetic: true
 } {
   return {
     type: "text",
     text: `${text}\n${OMO_INTERNAL_INITIATOR_MARKER}`,
-    synthetic: true,
   }
 }